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Comment by goerch | Hacker News Reader

Theoretically I would agree, but practically I still wonder why we need different database engines for row and columnar storage if supporting different types of indices is trivial(TM) for Postgres?

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There are definitely hybrid OLTP-OLAP databases, or HTAP (Hybrid Transaction and Analytical Processing). Microsoft and, I believe, Oracle both have HTAP tech.

The most novel design, I think, is CedarDB (developed by Thomas Neumann's database group at TUM), which adaptively stores both row and column versions of the data [1], where some data is permanently compressed to columnar format and hot rows are converted "just in time" to columnar data as needed.

[1] https://cedardb.com/blog/colibri/

In theory, you don't. In practice, it's because the major SQL DBMS were architected around row-oriented storage and the technical effort to implement hybrid storage is large.

There are columnar storage engine extensions for many of the popular databases, though.

Interesting: I transferred the idea of a matrix being stored row or column wise to the database world and assumed this was a more physical than theoretical feature (not a native speaker here)?

Looking forward to check out `pg_duckdb`, yes.

there are hybrid engines too, so-called HTAP (as opposed to OLAP or OLTP) notable efforts are: SingleStore (commercial) and OceanBase (foss)

Microsoft SQL Server can use both row and column store for tables, in various combinations such as row store for the table with a columnar index, or vice versa.

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